ASTRONOMICAL REFRACTION MODEL BY LEAST SQUARE FITTING ABOVE KUFA ASTRONOMICAL OBSERVATORY

In the domains of Astronomy and Geodesy, and according to the different hypotheses dependent on distribution of atmospheric condition , many versions of the computing formulae of Atmospheric refraction have been published, and a lot of versions of Atmospheric refraction tables have also come out to get important and more accurate information. In this study a new mathematical model has been proposed to calculate the Astronomic refraction by using least square fitting method and other mathematical approximations with utilizing data that was collected by the weather link station accompanying Kufa Astronomical Observatory, during the interval (152011 to 3042012). In this model Astronomic refraction in (arc sec ), when: P in (hPa) , T in (0C ) , and the altitude in (deg); also is applicable for altitude range 10 - 300 (zenith angle from 600 to 900) in comparison with the previous Astronomic refraction models. Thus, the Astronomic refraction value (in arc sec) is presented at weather conditions (T0=100C, P0=1005(hpa)) and zenith angles (600,650,700,750,800,850 ) equals to (100.985, 122.504, 154.770, 208.515, 315.891, 637.192) respectively. The results obtained from the study have been compared with other researchers which was in perfect agreement .